Print output of predictions in simple estimator example for DistributionStrategy

Resolved the TODO that asked to print meaningful results from the Estimator's predictions.
Collects all elements yielded by the generator in a list and prints that list instead of the generator object.
Results in the following output: `Prediction results: [{'logits': array([1.0162734], dtype=float32)}, ..., {'logits': array([1.0162734], dtype=float32)}]`.